A motor assembly usually comprises a motor and a gearbox. The motor comprises a motor shaft which is supported by bearings fixed in a motor housing. One end of the motor shaft protrudes from one end cap of the motor housing from a first bearing fixed in the end cap and extends to a second bearing fixed in the gearbox. The motor shaft comprises a worm located between the first and second bearings. The worm rotates with the motor shaft and is used to drive a worm gear of the gearbox.
As is known, the motor shaft will receive a reaction force from the worm gear when the worm drives the worm gear or when the worm is driven by the worm gear. The reaction force may be sufficient to bend the motor shaft resulting in vibration and noise. When the motor shaft is bent, the worm will not match the worm gear well any more, which will lower or disable the self-locking ability between the worm and the worm gear. The self-locking ability is the characteristic which prevents the worm wheel from driving the motor. This is desirable in some applications for example due to safety and security issues where the motor assembly moves a load but an external force applied to the load will not move the load.
One solution to overcome the above problem is to use a larger motor shaft. However, the size of the motor, the worm and the gearbox will be increased to match the larger motor shaft, which will make the motor assembly larger, heavier and cost more.
Therefore, there is a desirable for an improved motor assembly with a strengthened motor shaft and a small size.